Cell equalization system

Abstract

A cell equalization system includes: a battery including a plurality of chargeable cells connected in series and mounted on a vehicle; a battery ECU configured to control the battery; an equalization circuit configured to perform equalization of remaining capacity variation of the plurality of cells; and an equalization control unit configured to control the equalization circuit. The battery ECU is configured to calculate the remaining capacity variation at startup of ECU in which the battery ECU changes from a sleep state to a startup state. The cell equalization system is configured to execute first equalization processing for performing the equalization when the battery ECU is in the startup state, and second equalization processing for performing the equalization when the battery ECU is in the sleep state.

What is claimed is: 
     
       1. A cell equalization system comprising:
 a battery including a plurality of chargeable cells connected in series and mounted on a vehicle; 
 a battery ECU configured to control the battery; 
 an equalization circuit configured to perform equalization of remaining capacity variation of the plurality of cells; and 
 an equalization control unit configured to control the equalization circuit, wherein 
 the battery ECU is configured to calculate the remaining capacity variation at startup of the battery ECU in which the battery ECU changes from a sleep state to a startup state, and 
 the cell equalization system is configured to execute
 first equalization processing for performing the equalization when the battery ECU is in the startup state, and 
 second equalization processing for performing the equalization when the battery ECU is in the sleep state, wherein 
 
 the cell equalization system is configured to execute
 the first equalization processing when the remaining capacity variation is equal to or greater than a first threshold value, and 
 the second equalization processing when the remaining capacity variation is equal to or greater than a second threshold value which is smaller than the first threshold value. 
 
 
     
     
       2. The cell equalization system according to  claim 1 , wherein
 the first threshold value is set based on an abnormality determination threshold value related to the remaining capacity variation and an estimation error of the remaining capacity variation. 
 
     
     
       3. The cell equalization system according to  claim 2 , wherein
 when determining that the second equalization processing is necessary, the battery ECU calculates an operation time based on a maximum value of the remaining capacity variation, which is a largest variation of remaining capacity among the remaining capacity variation of the plurality of cells at the startup of ECU, the second threshold value, and an equalization current. 
 
     
     
       4. The cell equalization system according to  claim 3 , wherein
 in the second equalization processing, the battery ECU maintains the sleep state, and the equalization control unit executes the equalization until the operation time elapses. 
 
     
     
       5. The cell equalization system according to  claim 2 , wherein
 the cell equalization system is configured to execute the second equalization processing after the first equalization processing, and 
 the battery ECU is configured to
 calculate an operation time of the first equalization processing based on a maximum value of the remaining capacity variation, which is a largest variation of remaining capacity among the remaining capacity variation of the plurality of cells at the startup of the ECU, the first threshold value, and an equalization current, 
 calculate the maximum value of the remaining capacity variation immediately before sleep of ECU in which the battery ECU changes from the startup state to the sleep state based on the maximum value of the remaining capacity variation at the startup of ECU, the operation time of the first equalization processing, and the equalization current, and 
 calculate an operation time of the second equalization processing after the first equalization processing based on the calculated maximum value of the remaining capacity variation, the second threshold value, and the equalization current. 
 
 
     
     
       6. The cell equalization system according to  claim 1 , wherein
 the battery ECU is configured
 to calculate the remaining capacity variation when an elapsed time from ignition off to the startup state exceeds a predetermined time, and 
 not to calculate the remaining capacity variation when the elapsed time is less than the predetermined time. 
 
 
     
     
       7. The cell equalization system according to  claim 6 , wherein
 the battery ECU is configured to
 determine whether the equalization is necessary based on the remaining capacity variation when the remaining capacity variation is calculated at the startup of ECU, and 
 determine whether the equalization is necessary based on the remaining capacity variation calculated last time when the remaining capacity variation is not calculated at the startup of ECU. 
 
 
     
     
       8. A cell equalization system comprising:
 a battery including a plurality of chargeable cells connected in series and mounted on a vehicle; 
 a battery ECU configured to control the battery; 
 an equalization circuit configured to perform equalization of remaining capacity variation of the plurality of cells; and 
 an equalization control unit configured to control the equalization circuit, wherein 
 the battery ECU is configured to calculate the remaining capacity variation at startup of the battery ECU in which the battery ECU changes from a sleep state to a startup state, 
 the cell equalization system is configured to execute
 first equalization processing for performing the equalization when the battery ECU is in the startup state, and 
 second equalization processing for performing the equalization when the battery ECU is in the sleep state, and 
 
 the battery ECU is configured to prohibit the first equalization processing during external charging of the battery and during constant voltage control.